// Copyright (c) 2021, gottingen group.
// All rights reserved.
// Created by liyinbin lijippy@163.com
//
// -----------------------------------------------------------------------------
// File: btree_set.h
// -----------------------------------------------------------------------------
//
// This header file defines B-tree sets: sorted associative containers of
// values.
//
//     * `abel::btree_set<>`
//     * `abel::btree_multiset<>`
//
// These B-tree types are similar to the corresponding types in the STL
// (`std::set` and `std::multiset`) and generally conform to the STL interfaces
// of those types. However, because they are implemented using B-trees, they
// are more efficient in most situations.
//
// Unlike `std::set` and `std::multiset`, which are commonly implemented using
// red-black tree nodes, B-tree sets use more generic B-tree nodes able to hold
// multiple values per node. Holding multiple values per node often makes
// B-tree sets perform better than their `std::set` counterparts, because
// multiple entries can be checked within the same cache hit.
//
// However, these types should not be considered drop-in replacements for
// `std::set` and `std::multiset` as there are some API differences, which are
// noted in this header file.
//
// Importantly, insertions and deletions may invalidate outstanding iterators,
// pointers, and references to elements. Such invalidations are typically only
// an issue if insertion and deletion operations are interleaved with the use of
// more than one iterator, pointer, or reference simultaneously. For this
// reason, `insert()` and `erase()` return a valid iterator at the current
// position.

#ifndef ABEL_CONTAINER_BTREE_SET_H_
#define ABEL_CONTAINER_BTREE_SET_H_

#include "abel/container/internal/btree.h"  // IWYU pragma: export
#include "abel/container/internal/btree_container.h"  // IWYU pragma: export

namespace abel {


// abel::btree_set<>
//
// An `abel::btree_set<K>` is an ordered associative container of unique key
// values designed to be a more efficient replacement for `std::set` (in most
// cases).
//
// Keys are sorted using an (optional) comparison function, which defaults to
// `std::less<K>`.
//
// An `abel::btree_set<K>` uses a default allocator of `std::allocator<K>` to
// allocate (and deallocate) nodes, and construct and destruct values within
// those nodes. You may instead specify a custom allocator `A` (which in turn
// requires specifying a custom comparator `C`) as in
// `abel::btree_set<K, C, A>`.
//
template<typename Key, typename Compare = std::less<Key>,
        typename Alloc = std::allocator<Key>>
class btree_set
        : public container_internal::btree_set_container<
                container_internal::btree < container_internal::set_params <
                Key, Compare, Alloc, /*TargetNodeSize=*/256,
                /*Multi=*/false>>

> {
using Base = typename btree_set::btree_set_container;

public:

// Constructors and Assignment Operators
//
// A `btree_set` supports the same overload set as `std::set`
// for construction and assignment:
//
// * Default constructor
//
//   abel::btree_set<std::string> set1;
//
// * Initializer List constructor
//
//   abel::btree_set<std::string> set2 =
//       {{"huey"}, {"dewey"}, {"louie"},};
//
// * Copy constructor
//
//   abel::btree_set<std::string> set3(set2);
//
// * Copy assignment operator
//
//  abel::btree_set<std::string> set4;
//  set4 = set3;
//
// * Move constructor
//
//   // Move is guaranteed efficient
//   abel::btree_set<std::string> set5(std::move(set4));
//
// * Move assignment operator
//
//   // May be efficient if allocators are compatible
//   abel::btree_set<std::string> set6;
//   set6 = std::move(set5);
//
// * Range constructor
//
//   std::vector<std::string> v = {"a", "b"};
//   abel::btree_set<std::string> set7(v.begin(), v.end());
btree_set() {}

using Base::Base;

// btree_set::begin()
//
// Returns an iterator to the beginning of the `btree_set`.
using Base::begin;

// btree_set::cbegin()
//
// Returns a const iterator to the beginning of the `btree_set`.
using Base::cbegin;

// btree_set::end()
//
// Returns an iterator to the end of the `btree_set`.
using Base::end;

// btree_set::cend()
//
// Returns a const iterator to the end of the `btree_set`.
using Base::cend;

// btree_set::empty()
//
// Returns whether or not the `btree_set` is empty.
using Base::empty;

// btree_set::max_size()
//
// Returns the largest theoretical possible number of elements within a
// `btree_set` under current memory constraints. This value can be thought
// of as the largest value of `std::distance(begin(), end())` for a
// `btree_set<Key>`.
using Base::max_size;

// btree_set::size()
//
// Returns the number of elements currently within the `btree_set`.
using Base::size;

// btree_set::clear()
//
// Removes all elements from the `btree_set`. Invalidates any references,
// pointers, or iterators referring to contained elements.
using Base::clear;

// btree_set::erase()
//
// Erases elements within the `btree_set`. Overloads are listed below.
//
// iterator erase(iterator position):
// iterator erase(const_iterator position):
//
//   Erases the element at `position` of the `btree_set`, returning
//   the iterator pointing to the element after the one that was erased
//   (or end() if none exists).
//
// iterator erase(const_iterator first, const_iterator last):
//
//   Erases the elements in the open interval [`first`, `last`), returning
//   the iterator pointing to the element after the interval that was erased
//   (or end() if none exists).
//
// template <typename K> size_type erase(const K& key):
//
//   Erases the element with the matching key, if it exists, returning the
//   number of elements erased.
using Base::erase;

// btree_set::insert()
//
// Inserts an element of the specified value into the `btree_set`,
// returning an iterator pointing to the newly inserted element, provided that
// an element with the given key does not already exist. If an insertion
// occurs, any references, pointers, or iterators are invalidated.
// Overloads are listed below.
//
// std::pair<iterator,bool> insert(const value_type& value):
//
//   Inserts a value into the `btree_set`. Returns a pair consisting of an
//   iterator to the inserted element (or to the element that prevented the
//   insertion) and a bool denoting whether the insertion took place.
//
// std::pair<iterator,bool> insert(value_type&& value):
//
//   Inserts a moveable value into the `btree_set`. Returns a pair
//   consisting of an iterator to the inserted element (or to the element that
//   prevented the insertion) and a bool denoting whether the insertion took
//   place.
//
// iterator insert(const_iterator hint, const value_type& value):
// iterator insert(const_iterator hint, value_type&& value):
//
//   Inserts a value, using the position of `hint` as a non-binding suggestion
//   for where to begin the insertion search. Returns an iterator to the
//   inserted element, or to the existing element that prevented the
//   insertion.
//
// void insert(InputIterator first, InputIterator last):
//
//   Inserts a range of values [`first`, `last`).
//
// void insert(std::initializer_list<init_type> ilist):
//
//   Inserts the elements within the initializer list `ilist`.
using Base::insert;

// btree_set::emplace()
//
// Inserts an element of the specified value by constructing it in-place
// within the `btree_set`, provided that no element with the given key
// already exists.
//
// The element may be constructed even if there already is an element with the
// key in the container, in which case the newly constructed element will be
// destroyed immediately.
//
// If an insertion occurs, any references, pointers, or iterators are
// invalidated.
using Base::emplace;

// btree_set::emplace_hint()
//
// Inserts an element of the specified value by constructing it in-place
// within the `btree_set`, using the position of `hint` as a non-binding
// suggestion for where to begin the insertion search, and only inserts
// provided that no element with the given key already exists.
//
// The element may be constructed even if there already is an element with the
// key in the container, in which case the newly constructed element will be
// destroyed immediately.
//
// If an insertion occurs, any references, pointers, or iterators are
// invalidated.
using Base::emplace_hint;

// btree_set::extract()
//
// Extracts the indicated element, erasing it in the process, and returns it
// as a C++17-compatible node handle. Overloads are listed below.
//
// node_type extract(const_iterator position):
//
//   Extracts the element at the indicated position and returns a node handle
//   owning that extracted data.
//
// template <typename K> node_type extract(const K& x):
//
//   Extracts the element with the key matching the passed key value and
//   returns a node handle owning that extracted data. If the `btree_set`
//   does not contain an element with a matching key, this function returns an
//   empty node handle.
//
// NOTE: In this context, `node_type` refers to the C++17 concept of a
// move-only type that owns and provides access to the elements in associative
// containers (https://en.cppreference.com/w/cpp/container/node_handle).
// It does NOT refer to the data layout of the underlying btree.
using Base::extract;

// btree_set::merge()
//
// Extracts elements from a given `source` btree_set into this
// `btree_set`. If the destination `btree_set` already contains an
// element with an equivalent key, that element is not extracted.
using Base::merge;

// btree_set::swap(btree_set& other)
//
// Exchanges the contents of this `btree_set` with those of the `other`
// btree_set, avoiding invocation of any move, copy, or swap operations on
// individual elements.
//
// All iterators and references on the `btree_set` remain valid, excepting
// for the past-the-end iterator, which is invalidated.
using Base::swap;

// btree_set::contains()
//
// template <typename K> bool contains(const K& key) const:
//
// Determines whether an element comparing equal to the given `key` exists
// within the `btree_set`, returning `true` if so or `false` otherwise.
//
// Supports heterogeneous lookup, provided that the set is provided a
// compatible heterogeneous comparator.
using Base::contains;

// btree_set::count()
//
// template <typename K> size_type count(const K& key) const:
//
// Returns the number of elements comparing equal to the given `key` within
// the `btree_set`. Note that this function will return either `1` or `0`
// since duplicate elements are not allowed within a `btree_set`.
//
// Supports heterogeneous lookup, provided that the set is provided a
// compatible heterogeneous comparator.
using Base::count;

// btree_set::equal_range()
//
// Returns a closed range [first, last], defined by a `std::pair` of two
// iterators, containing all elements with the passed key in the
// `btree_set`.
using Base::equal_range;

// btree_set::find()
//
// template <typename K> iterator find(const K& key):
// template <typename K> const_iterator find(const K& key) const:
//
// Finds an element with the passed `key` within the `btree_set`.
//
// Supports heterogeneous lookup, provided that the set is provided a
// compatible heterogeneous comparator.
using Base::find;

// btree_set::get_allocator()
//
// Returns the allocator function associated with this `btree_set`.
using Base::get_allocator;

// btree_set::key_comp();
//
// Returns the key comparator associated with this `btree_set`.
using Base::key_comp;

// btree_set::value_comp();
//
// Returns the value comparator associated with this `btree_set`. The keys to
// sort the elements are the values themselves, therefore `value_comp` and its
// sibling member function `key_comp` are equivalent.
using Base::value_comp;
};

// abel::swap(abel::btree_set<>, abel::btree_set<>)
//
// Swaps the contents of two `abel::btree_set` containers.
template<typename K, typename C, typename A>
void swap(btree_set <K, C, A> &x, btree_set <K, C, A> &y) {
    return x.swap(y);
}

// abel::erase_if(abel::btree_set<>, Pred)
//
// Erases all elements that satisfy the predicate pred from the container.
template<typename K, typename C, typename A, typename Pred>
void erase_if(btree_set <K, C, A> &set, Pred pred) {
    for (auto it = set.begin(); it != set.end();) {
        if (pred(*it)) {
            it = set.erase(it);
        } else {
            ++it;
        }
    }
}

// abel::btree_multiset<>
//
// An `abel::btree_multiset<K>` is an ordered associative container of
// keys and associated values designed to be a more efficient replacement
// for `std::multiset` (in most cases). Unlike `abel::btree_set`, a B-tree
// multiset allows equivalent elements.
//
// Keys are sorted using an (optional) comparison function, which defaults to
// `std::less<K>`.
//
// An `abel::btree_multiset<K>` uses a default allocator of `std::allocator<K>`
// to allocate (and deallocate) nodes, and construct and destruct values within
// those nodes. You may instead specify a custom allocator `A` (which in turn
// requires specifying a custom comparator `C`) as in
// `abel::btree_multiset<K, C, A>`.
//
template<typename Key, typename Compare = std::less<Key>,
        typename Alloc = std::allocator<Key>>
class btree_multiset
        : public container_internal::btree_multiset_container<
                container_internal::btree < container_internal::set_params <
                Key, Compare, Alloc, /*TargetNodeSize=*/256,
                /*Multi=*/true>>

> {
using Base = typename btree_multiset::btree_multiset_container;

public:

// Constructors and Assignment Operators
//
// A `btree_multiset` supports the same overload set as `std::set`
// for construction and assignment:
//
// * Default constructor
//
//   abel::btree_multiset<std::string> set1;
//
// * Initializer List constructor
//
//   abel::btree_multiset<std::string> set2 =
//       {{"huey"}, {"dewey"}, {"louie"},};
//
// * Copy constructor
//
//   abel::btree_multiset<std::string> set3(set2);
//
// * Copy assignment operator
//
//  abel::btree_multiset<std::string> set4;
//  set4 = set3;
//
// * Move constructor
//
//   // Move is guaranteed efficient
//   abel::btree_multiset<std::string> set5(std::move(set4));
//
// * Move assignment operator
//
//   // May be efficient if allocators are compatible
//   abel::btree_multiset<std::string> set6;
//   set6 = std::move(set5);
//
// * Range constructor
//
//   std::vector<std::string> v = {"a", "b"};
//   abel::btree_multiset<std::string> set7(v.begin(), v.end());
btree_multiset() {}

using Base::Base;

// btree_multiset::begin()
//
// Returns an iterator to the beginning of the `btree_multiset`.
using Base::begin;

// btree_multiset::cbegin()
//
// Returns a const iterator to the beginning of the `btree_multiset`.
using Base::cbegin;

// btree_multiset::end()
//
// Returns an iterator to the end of the `btree_multiset`.
using Base::end;

// btree_multiset::cend()
//
// Returns a const iterator to the end of the `btree_multiset`.
using Base::cend;

// btree_multiset::empty()
//
// Returns whether or not the `btree_multiset` is empty.
using Base::empty;

// btree_multiset::max_size()
//
// Returns the largest theoretical possible number of elements within a
// `btree_multiset` under current memory constraints. This value can be
// thought of as the largest value of `std::distance(begin(), end())` for a
// `btree_multiset<Key>`.
using Base::max_size;

// btree_multiset::size()
//
// Returns the number of elements currently within the `btree_multiset`.
using Base::size;

// btree_multiset::clear()
//
// Removes all elements from the `btree_multiset`. Invalidates any references,
// pointers, or iterators referring to contained elements.
using Base::clear;

// btree_multiset::erase()
//
// Erases elements within the `btree_multiset`. Overloads are listed below.
//
// iterator erase(iterator position):
// iterator erase(const_iterator position):
//
//   Erases the element at `position` of the `btree_multiset`, returning
//   the iterator pointing to the element after the one that was erased
//   (or end() if none exists).
//
// iterator erase(const_iterator first, const_iterator last):
//
//   Erases the elements in the open interval [`first`, `last`), returning
//   the iterator pointing to the element after the interval that was erased
//   (or end() if none exists).
//
// template <typename K> size_type erase(const K& key):
//
//   Erases the elements matching the key, if any exist, returning the
//   number of elements erased.
using Base::erase;

// btree_multiset::insert()
//
// Inserts an element of the specified value into the `btree_multiset`,
// returning an iterator pointing to the newly inserted element.
// Any references, pointers, or iterators are invalidated.  Overloads are
// listed below.
//
// iterator insert(const value_type& value):
//
//   Inserts a value into the `btree_multiset`, returning an iterator to the
//   inserted element.
//
// iterator insert(value_type&& value):
//
//   Inserts a moveable value into the `btree_multiset`, returning an iterator
//   to the inserted element.
//
// iterator insert(const_iterator hint, const value_type& value):
// iterator insert(const_iterator hint, value_type&& value):
//
//   Inserts a value, using the position of `hint` as a non-binding suggestion
//   for where to begin the insertion search. Returns an iterator to the
//   inserted element.
//
// void insert(InputIterator first, InputIterator last):
//
//   Inserts a range of values [`first`, `last`).
//
// void insert(std::initializer_list<init_type> ilist):
//
//   Inserts the elements within the initializer list `ilist`.
using Base::insert;

// btree_multiset::emplace()
//
// Inserts an element of the specified value by constructing it in-place
// within the `btree_multiset`. Any references, pointers, or iterators are
// invalidated.
using Base::emplace;

// btree_multiset::emplace_hint()
//
// Inserts an element of the specified value by constructing it in-place
// within the `btree_multiset`, using the position of `hint` as a non-binding
// suggestion for where to begin the insertion search.
//
// Any references, pointers, or iterators are invalidated.
using Base::emplace_hint;

// btree_multiset::extract()
//
// Extracts the indicated element, erasing it in the process, and returns it
// as a C++17-compatible node handle. Overloads are listed below.
//
// node_type extract(const_iterator position):
//
//   Extracts the element at the indicated position and returns a node handle
//   owning that extracted data.
//
// template <typename K> node_type extract(const K& x):
//
//   Extracts the element with the key matching the passed key value and
//   returns a node handle owning that extracted data. If the `btree_multiset`
//   does not contain an element with a matching key, this function returns an
//   empty node handle.
//
// NOTE: In this context, `node_type` refers to the C++17 concept of a
// move-only type that owns and provides access to the elements in associative
// containers (https://en.cppreference.com/w/cpp/container/node_handle).
// It does NOT refer to the data layout of the underlying btree.
using Base::extract;

// btree_multiset::merge()
//
// Extracts elements from a given `source` btree_multiset into this
// `btree_multiset`. If the destination `btree_multiset` already contains an
// element with an equivalent key, that element is not extracted.
using Base::merge;

// btree_multiset::swap(btree_multiset& other)
//
// Exchanges the contents of this `btree_multiset` with those of the `other`
// btree_multiset, avoiding invocation of any move, copy, or swap operations
// on individual elements.
//
// All iterators and references on the `btree_multiset` remain valid,
// excepting for the past-the-end iterator, which is invalidated.
using Base::swap;

// btree_multiset::contains()
//
// template <typename K> bool contains(const K& key) const:
//
// Determines whether an element comparing equal to the given `key` exists
// within the `btree_multiset`, returning `true` if so or `false` otherwise.
//
// Supports heterogeneous lookup, provided that the set is provided a
// compatible heterogeneous comparator.
using Base::contains;

// btree_multiset::count()
//
// template <typename K> size_type count(const K& key) const:
//
// Returns the number of elements comparing equal to the given `key` within
// the `btree_multiset`.
//
// Supports heterogeneous lookup, provided that the set is provided a
// compatible heterogeneous comparator.
using Base::count;

// btree_multiset::equal_range()
//
// Returns a closed range [first, last], defined by a `std::pair` of two
// iterators, containing all elements with the passed key in the
// `btree_multiset`.
using Base::equal_range;

// btree_multiset::find()
//
// template <typename K> iterator find(const K& key):
// template <typename K> const_iterator find(const K& key) const:
//
// Finds an element with the passed `key` within the `btree_multiset`.
//
// Supports heterogeneous lookup, provided that the set is provided a
// compatible heterogeneous comparator.
using Base::find;

// btree_multiset::get_allocator()
//
// Returns the allocator function associated with this `btree_multiset`.
using Base::get_allocator;

// btree_multiset::key_comp();
//
// Returns the key comparator associated with this `btree_multiset`.
using Base::key_comp;

// btree_multiset::value_comp();
//
// Returns the value comparator associated with this `btree_multiset`. The
// keys to sort the elements are the values themselves, therefore `value_comp`
// and its sibling member function `key_comp` are equivalent.
using Base::value_comp;
};

// abel::swap(abel::btree_multiset<>, abel::btree_multiset<>)
//
// Swaps the contents of two `abel::btree_multiset` containers.
template<typename K, typename C, typename A>
void swap(btree_multiset < K, C, A > &x, btree_multiset < K, C, A > &y) {
    return x.swap(y);
}

// abel::erase_if(abel::btree_multiset<>, Pred)
//
// Erases all elements that satisfy the predicate pred from the container.
template<typename K, typename C, typename A, typename Pred>
void erase_if(btree_multiset < K, C, A > &set, Pred
pred) {
for (
auto it = set.begin();
it != set.

end();

) {
if (
pred(*it)
) {
it = set.erase(it);
} else {
++
it;
}
}
}


}  // namespace abel

#endif  // ABEL_CONTAINER_BTREE_SET_H_
